PHP - Memcache Functions

The Memcache module can provide a handy procedural and object-oriented interface to Memcached, a highly effective caching daemon that was specially designed to decrease database load in dynamic web applications.

The Memcache module can also provide a session handler (Memcache).

For more information about Memcached can be found at » http://www.danga.com/memcached/.

Installation

This PECL extension has not been included with PHP. Additional information such as new versions, downloads, source files, developer information, and CHANGELOG can be found here: »https://pecl.php.net/package/memcache.

To use these functions, we must compile PHP with memcache support by using the --enable-memcache [= DIR] option. We may optionally disable memcache session handler support by specifying --disable-memcache-session.

Windows users can enable php_memcache.dll inside php.ini to use these functions. We need to download the DLL of this PECL extension from the »PHP Downloads or » http://snaps.php.net/page.

Requirements

Memcache module can use the functions of » zlib to support on-the-fly data compression. The Zlib has required to install this module.

Resource Types

There is only one resource type used in the emcache module - it's the link identifier for cache server connection.

PHP 4.3.3 or newer has required to use the Memcache extension.

Runtime Configuration

The behavior of these functions can depend on settings in php.ini.

Memcache Configuration Options

Name	Default	Changeable	Changelog
memcache.allow_failover	"1"	PHP_INI_ALL	Available since memcache 2.0.2.
memcache.max_failover_attempts	"20"	PHP_INI_ALL	Available since memcache 2.1.0.
memcache.chunk_size	"8192"	PHP_INI_ALL	Available since memcache 2.0.2.
memcache.default_port	"11211"	PHP_INI_ALL	Available since memcache 2.0.2.
memcache.hash_strategy	"standard"	PHP_INI_ALL	Available since memcache 2.2.0.
memcache.hash_function	"crc32"	PHP_INI_ALL	Available since memcache 2.2.0.
session.save_handler	"files"	PHP_INI_ALL	Supported since memcache 2.1.2
session.save_path	""	PHP_INI_ALL	Supported since memcache 2.1.2
memcache.protocol	ascii	>PHP_INI_ALL	Supported since memcache 3.0.0
memcache.redundancy	1	>PHP_INI_ALL	Supported since memcache 3.0.0
memcache.session_redundancy	2	>PHP_INI_ALL	Supported since memcache 3.0.0
memcache.compress_threshold	20000	>PHP_INI_ALL	Supported since memcache 3.0.3
memcache.lock_timeout	15	>PHP_INI_ALL	Supported since memcache 3.0.4

For a detailed description of the PHP_INI_* constants, refer to the documentation Where a configuration setting may be set.

memcache.allow_failover boolean − Whether to transparently failover to other servers on errors.
memcache.max_failover_attempts integer − Defines how many servers to try when setting and getting data. Used only in conjunction with memcache.allow_failover.
memcache.chunk_size integer − Data will be transferred in chunks of this size, setting the value lower requires more network writes. Try increasing this value to 32768 if noticing otherwise inexplicable slowdowns.
memcache.default_port string − The default TCP port number to use when connecting to the memcached server if no other port is specified.
memcache.hash_strategy string − Controls which strategy to use when mapping keys to servers. Set this value to consistent to enable consistent hashing which allows servers to be added or removed from the pool without causing keys to be remapped. Setting this value to standard results in the old strategy being used.
memcache.hash_function string − Controls which hash function to apply when mapping keys to servers, crc32 uses the standard CRC32 hash while fnv uses FNV-1a.
session.save_handler string − Use memcache as a session handler by setting this value to memcache.
session.save_path string − Defines a comma separated of server urls to use for session storage, for example "tcp://host1:11211, tcp://host2:11211". Each url may contain parameters which are applied to that server, they are the same as for the Memcache::addServer() method. For example "tcp://host1:11211?persistent=1&weight=1&timeout=1&retry_interval=15"
memcache.protocol string
memcache.redundancy integer
memcache.session_redundancy integer
memcache.compress_threshold integer
memcache.lock_timeout integer

Basic usage

In this example, an object is being saved in a cache and then retrieved back. Object and other non-scalar types are serialized before saving, so it's impossible to store resources (i.e. connection identifiers and others) in a cache.

Example 1

<?php
   $memcache = new Memcache;
   $memcache->connect("localhost", 11211) or die ("Could not connect");
   $version = $memcache->getVersion();
   
   echo "Server's version: ".$version."<br/>\n";

   $tmp_object = new stdClass;
   $tmp_object->str_attr = "test";
   $tmp_object->int_attr = 123;
   $memcache->set("key", $tmp_object, false, 10) or die ("Failed to save data at the server");
   echo "Store data in the cache (data will expire in 10 seconds) <br/>\n";

   $get_result = $memcache->get("key");
   echo "Data from the cache: <br/>\n";

   var_dump($get_result);
?>

Using memcache session handler

Example 2

<?php
   $session_save_path = "tcp://$host:$port?persistent=1&weight=2&timeout=2&retry_interval=10,,tcp://$host:$port"; 

   ini_set("session.save_handler", "memcache"); 
   ini_set("session.save_path", $session_save_path); 
?>

Predefined Constants

Memcache Constants

Sr.No	Name & Description
1	MEMCACHE_COMPRESSED (integer) Used to turn on-the-fly data compression on with Memcache::set(), Memcache::add() and Memcache::replace().
2	PMEMCACHE_HAVE_SESSION (integer) 1 if this Memcache session handler is available, 0 otherwise.
3	MEMCACHE_USER1 (integer) Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().
4	MEMCACHE_USER2 (integer) Used to trn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().
5	MEMCACHE_USER3 (integer) Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().
6	MEMCACHE_USER4 (integer) Used to turn user-defined application flag on with Memcache::set(), Memcache::add() and Memcache::replace().

Memcache Functions

Following are the Memcache functions −

Sr.No	Function & Description
1	Memcache::add() This function can add an item to server.
2	Memcache::addServer() This function can add a memcached server to connection pool.
3	Memcache::close() This function can close the memcached server connection.
4	Memcache::connect() This function can open a memcached server connection.
5	memcache_debug() This function can turn debug output on/off.
6	Memcache::decrement() This function can decrement the item's value.
7	Memcache::delete() This function can delete an item from the server.
8	Memcache::flush() This function can flush all existing items at the server.
9	Memcache::get() This function can retrieve an item from the server.
10	Memcache::getExtendedStats() This function can get the statistics from all servers in a pool.
11	Memcache::getServerStatus() This function can return the server status.
12	Memcache::getStats() This function can get the statistics of the server.
13	Memcache::getVersion() This function can return the version of the server.
14	Memcache::increment() This function can increment the item's value.
15	Memcache::pconnect() This function can open a memcached server persistent connection.
16	Memcache::replace() This function can replace the value of an existing item.
17	Memcache::set() This function can store the data at the server.
18	Memcache::setCompressThreshold() This function can enable an automatic compression of large values.
19	Memcache::setServerParams() This function can change the server parameters and status at runtime.

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